When an emergency event, e.g., a natural disaster (such as an earthquake) or a terrorist attack, occurs, telecommunication networks serving the region involved in the emergency event may become overloaded or congested due to dramatically increased network traffics, and possibly, damages to telecommunication infrastructures.
For example, users may attempt to call their relatives or friends who were possibly in that region when the emergency event occurred to confirm whether they are fine or not. However, due to a possible network congestion, the call success rate may be very low and thus many of such attempts may fail. In this case, a large number of re-attempts will be made, which makes the situation even worse.
Some solutions have been proposed for network overload protection. In one solution for example, a network or a network node can be prevented from being overloaded by simply rejecting or discarding further traffic when the load on the network or network node is higher than a predefined threshold. As another example, a telecommunication operator may broadcast messages to its subscribers, asking them to stop making calls to the region involved in the emergency event, so as to avoid network overload or congestion. However, these solutions cannot relief the anxiety of people and thus lead to a poor user experience.
There is thus a need for a technique for informing a user who has failed his/her call attempt towards a region involved in an emergency event.